Air feed nut runner having a travelling gear case

ABSTRACT

A nut-running tool having a work spindle arranged in a supporting base so as to be advanced by a pneumatically powered piston into engagement with a threaded fastener. As the spindle advances, it is also rotated so as to drive the fastener into the work by means of an air-driven motor acting through a travelling gear train structure. A check cylinder is automatically operable at a predetermined time during the advance of the spindle so as to dampen the advancing speed of the spindle and thereby prevent the latter from ramming into the fastener. A spring-cushioned pin and slot connection between the gear train structure and the spindle permits the gear train structure to advance briefly relative to the spindle when the latter seats upon the fastener. This relative movement stops prior to the time that the fastener is driven into the work. A limit switch is arranged to automatically signal a control circuit when the spindle has completed its advance stroke. The time of operation of the switch may be adjusted. The control circuit responds to the signal to shut off air feed to the piston and motor. A spring responds to the latter action to retract the piston to its normal start position. A second limit switch is arranged to automatically signal the control circuit when the spindle has completed its retract stroke. The control circuit responds to the latter signal to recondition the circuit for the next cycle of operation.

United States Patent [72] Inventor Raymond .LSchaedler Utica, N.Y.

[21] Appl. No. 804,192

[22] Filed Mar. 4, 1969 [45] Patented Apr. 27, 197] [73 1 AssigneeChicago Pneumatic Tool Company New York, NY.

[54] AIR FEED NUT RUNNER HAVING A TRAVELLING Primary Examiner-Ernest R.Purser An0meyStephen J. Rudy ABSTRACT: A nut-running tool having a workspindle arranged in a supporting base so as to be advanced by apneumatically powered piston into engagement with a threaded fastener.As the spindle advances, it is also rotated so as to drive the fastenerinto the work by means of an airdriven motor acting through a travellinggear train structure. A check cylinder is automatically operable at apredetermined time during the advance of the spindle so as to dampen theadvancing speed of the spindle and thereby prevent the latter fromramming into the fastener. A spring-cushioned pin and slot connectionbetween the gear train structure and the spindle permits the gear trainstructure to advance briefly relative to the spindle when the latterseats upon the fastener. This relative movement stops prior to the timethat the fastener is driven into the work. A limit switch is arranged toautomatically signal a control circuit when the spindle has completedits advance stroke. The time of operation of the switch may be adjusted.The control circuit responds to the signal to shut off air feed to thepiston and motor. A spring responds to the latter action to retract thepiston to its normal start position. A second limit switch is arrangedto automatically signal the control circuit when the spindle hascompleted its retract stroke. The control circuit responds to the lattersignal to recondition the circuit for the next cycle of operation.

PATENTEU m2? 15m SHEET 2 OF 2 INVENTOR PAYMOA/0 SCH/450L519 ATTORNEY AIRFEED NUT RUNNER HAVING A TRAVELLING GEAR CIQE BACKGROUND OF THEINVENTION This invention relates to a nut-running tool of a type havinga work spindle which is advanced into engagement with a threadedfastener by means of a pneumatically powered piston, and wherein thespindle is simultaneously rotated by means of an air-driven motor todrive the fastener into the work. In the use of a tool of this type, thefastener is initially started by hand into the work.

A feature of the present invention is a travelling gear train structurewhich couples the spindle with the piston and also with the motor. ltadvances with the spindle and simultaneously transmits to it therotation of the motor.

Another feature of the present invention is a spring-loaded pin and slotconnection between the gear train structure and the spindle whichoperates upon seating of the work end of the spindle upon the fastenerto allow the gear train structure to advance briefly relative to thespindle while at the same time maintaining the spindle pressed under theload of the spring upon the fastener.

A further feature of the present invention is actuating means which iscooperable at a predetermined time during the travel of the gear trainstructure to actuate a dampening device so as to check the advancingspeed of the spindle before it engages with the fastener. This is ofadvantage in that it permits gentle engagement of the spindle with thefastener and avoids damage to the latter which might otherwise occurwere the spindle to advance under a high inertial load at a rapid rateinto the fastener.

A still further feature of the invention is an arrangement of switchelements which is automatically operable to signal a control circuitwhen the spindle has completed its advance stroke and also when thespindle has completed its return stroke.

BRIEF DESCRIPTION OF THE DRAWINGS In the accompanying drawings:

FlGS. l and IA which are in continuation of one another represent alongitudinal section through an air feed nut runner embodying theinvention;

FIG. 2 is a bottom plan of the supporting base and associated elements;

FIG. 3 is a section on line 3-3 of FIG. 1 with some portions brokenaway;

FIG. 4 is a detail of the V-coupling with the head end of the splinedshaft engaged therein;

FIG. 5 is a schematic showing of a gang of the tools in sideby-sidearrangement; and

FIG. 6 is a view similar to FIG. 5 but shows the tools in angular array.

DESCRIPTION OF PREFERRED EMBODIMENT The tool disclosed in the drawing asembodying the invention includes an oblong supporting base 10 havingparallel sidewalls 11, and upright front and rear end walls respectivelydesignated 12 and 13. A channel 14 is defined between the walls; itopens through the top and bottom areas of the base. The front face andthe bottom surface of the base are flat, either of which may be used formounting the tool to a stationary support. The outer surfaces of thesidewalls 11 are also flat whereby a gang of the tools may be arrangedupon a support in side-by-side relation as in FIG. 5. The front and rearwalls have upper triangular sections 15 and 16 extending in parallelrelation to each other above the level of the sidewalls. This triangularconfiguration enables a gang of the tools to be arranged in compactangular array upon a support as in FIG. 6. Because of this mountingcapacity of the tool, work requiring multiple fasteners therein to beset in close relation to one another may be subjected to the advantagesof a gang application of the tool.

A work spindle 17 is associated by means of an axially travelling gearcase 18 with a reciprocable piston 19 whereby the spindle may be axiallyadvanced and retracted relative to the work. The spindle is connectedthrough a gear train 21, supported within the gear case, with the driveof a rotary motor 22 whereby the spindle may be simultaneously rotatedas it is being advanced by the piston. The gear case is disposed in thechannel 14 of the supporting base; and it is limited therein to axialtravel between the end walls 12 and I3.

The motor 22 is of a conventional air-driven type. lts housing is fixedat its forward end (FIG. 1) by means of an adapter 23 to the rear wall13 of the base and extends axially rearward therefrom. lts drive shaft24 has a splined driving connection 25 with a coupling 26. The couplingin turn drivingly engages the head 27 of an elongated straight splinedshaft 28.

Here, the coupling (FIGS. 1, 4) is of a V-type. It has an annularforwardly extending skirt body 29 provided with a pair of diametricallyopposed V-slots 31, the wider ends of which slots open through theforward end of the coupling. The head 27 of the spline shaft has acylindrical body which is slidably received in the recess 32 of thecoupling and is formed with a pair of opposed wedge or V-ribs 33 on itssurface, which ribs are slidably seated in the V-slots. The spline shaft28 serves as a supporting rail for the travelling gear case [8 and alsoserves to transmit the drive of the motor through the gear train to thespindle. The spindle shaft extends axially with a sliding splineconnection 34 through a pinion member 35 of the gear train. The pinionis journaled in suitable bearings of the gear case. A smooth terminalcylindrical end portion 36 of the spline shaft is slidably received andsupported in a complementary recess 37 of a stub bearing shaft 38. Thelatter is retained by opposed nut and shoulder elements 39 and 41 in abearing 42 mounted in the front base wall 12. A compression spring 43,seated between the bottoms of recesses 37 and 45 respectively of thestub shaft 38 and the spline shaft 28, normally biases the spline shaftrearwardly so as to seat the head 27 of the spline shaft at the bottomof the V-slots of coupling 26, as in FIGS. 1 and 4.

An idler gear 46joumaled in the gear case drivingly engages pinion 35with a pinion part 47 of a pinion shaft 48. The latter is journaled inthe gear case. Pinion 35, gear 46, and pinion shaft 48 are suitablyrestrained in position endwise of the gear case by thrust bearings (notdesignated The gear case 18 has an axial forward tubular projection 49through which the pinion shah 48 extends into a spindle tube 5 l. Thelatter is relatively long. It is threadedly fixed at its rear end 52 inthe gear case projection 49; and slidably extends at its forward endthrough a bore 53 in the upper triangular front wall portion [5. Thework spindle 17 is slidably received in the spindle tube 51; and has atits rear end an internal axial sliding spline connection 54 with thepinion shaft 48 whereby rotation of the latter is transmitted to thespindle. Forwardly of the spline connection 54. a pin 55 anchored in thespindle extends transversely through a slot 56 in the pinion shaft. Acompression spring 57, limited between the rear end of the spindle and ashoulder of the pinion shaft, biases the spindle forwardly so as tolimit the pin 55 against the forward wall of the slot 56. in this normalcondition of the spindle, the forward end of the pinion shaft 48 islocated by the space 59. This space is about one-fourth of an inch inits axial dimension and is slightly less than the axial extent of theslot 56 at the rear of the pin. This pin and slot arrangement permitslimited forward movement of the pinion shaft relative to the spindle atcertain times during axial advance of the spindle as when the spindlesocket 61 (broken line) seats upon the head of a fastener preparatory todriving the fastener into the work. The relative forward movement of thepinion shaft at such times is cushioned by the spring 57 so as to avoidan undesirable strong thrust of the spindle against the fastener. Whenthe pinion shaft is relatively advanced in this action, its forward endwill limit against the recessed bottom 58 of the spindle; but the pin 55will not at any time engage the rear wall of slot 56. A bearing cage 62,threadedly engaged on the forward end of the spindle tube 51, provides asupporting bearing for a forward end portion of the spindle projectingbeyond the spindle tube.

The piston 19, which serves to advance the spindle. is reciprocable in acylinder 63. The latter is threadedly fixed by means of an adapter 64 atits forward end in a bore 65 of the rear upper triangular portion 16 ofthe base wall 13. The cylinder extends axially rearwardly from the basewall; and its longitudinal axis is parallel to and coplanar with that ofthe motor. A forward end of the piston is received in a rear tubularprojection 66 of a gear case cover 67. The latter is bolted fast to thegear case. The piston is rigidly retained in the tubular projection 66by means of a retaining bolt 68. A return spring 69 acting upon thepiston head 71 biases the piston to a normal retracted position, as inFlGS. 1, 1A, wherein the projection 66 of the gear case cover abuts astop 72 defined by a forward face of the rear base wall 13.

In the operation of the tool, live air fed concurrently to inlets 73 and74 respectively of the piston cylinder 63 and the housing of the motor22 advances the piston 19 and concurrently operates the motor. Rotationof the motor is transmitted through the spline shaft 28 and the geartrain 21 to the spindle 17. While the spindle is rotating, the pistonadvanca the gear case 18 slidingly along the spline shaft. The spindletube 51 and spindle advance forwardly as a unit with the gear case. Thespring load 43, acting on the spline shaft 28, normally maintains thehead end 27 of the latter seated in the coupling 26 and normallyrestrains the spline shaft from being frictionally carried along withthe travelling gear case. Eventually, the socket end 61 of the advancingspindle seats over the head of a fastener, not shown; (the fastener isinitially hand started into the work). As the socket seats upon thefastener, axial resistance offered by the fastener causes the pinionshaft 48 through the pin and slot connection 55, 56 to advance againstthe bias of the spring 57 to the extent of the space 59.

At times, because of burrs or nicks on the fastener, the fastener mayoffer more than normal torque resistance to its being entered into thework and may cause a reactionary torque to be transmitted back throughthe gear train 21 to the spline shaft 28. This reactionary load mayfrictionally bind or lock the pinion member 35 of the gear train to thespline shaft so as to prevent sliding travel of the gear case over thesplines 75 of the spline shaft. When this condition develops, the geartrain nevertheless continues to operate under the torque of the motor torotate the spindle. To avoid ineffective rotation of the spindle at thistime relative to the fastener without accompanying advancement of thespindle because of a locked condition of the gear case with the splineshaft, the particular V-coupling 26 has been provided between the motordrive and the spline shaft. The V-slots 31 of the coupling cooperatewith the V-ribs 33 of the head of the spline shaft under the developedtorque overload to force the head of the spline shaft forwardly in thecoupling. ln this action, the spline shaft advances axially into thestub bearing shaft 38 against the bias of the spring 43 and, as itadvances, it carries the gear case 18 with it to continue withoutinterruption advance and rotation of the spindle. Should the binding orlocked condition of the gear train and spline shaft become relaxed,spring 43 will respond to reseat the head end 27 of the spline shaft inthe coupling.

Under the force of the piston 19, the spindle initially advances at arapid rate toward the work. It is undesirable to have the spindle socket61 ram into the fastener at this rapid rate while under a high inertiaload. To avoid this, a conventional hydraulic check cylinder 76 isarranged in the base to check or dampen the advancing speed of thespindle at a predetermined distance before the spindle engages itssocket with the fastener. The check cylinder is pivoted at its forwardend 77 between the lower areas of the sidewalls of the base. It issupported at its opposite end by means of a collar 78 fitted in an axialbore 79 of the rear base wall 13. A plunger rod 81 of the check cylinderextends part way into bore 79 wherein it abuts the head end 82 of anactuating rod 83. The shank of the actuating rod extends with a slidefit through a switch support block 84 mounted in extension of the rearwall 13 of the base. An externally projecting threaded portion 85 of theactuating rod is threaded through the lower end 86 of a bar support 87.The upper end 88 of the support is slidably engaged upon the shank of anadvance control screw 89. A locknut 91 fixes the position of the supportbar upon the actuating rod. The control screw is relatively elongatedand passes slidably through the block 84 and the rear base wall 13 intothe channel 14 of the base 10 in parallel and coplanar relation to theactuating rod 83. The forward end of the control screw is threadedlyengaged in a nut 92 positioned in a bottom bifurcation 93 of the gearcase. A pin 94 restrains the nut in the bifurcation against relativerotation.

It can be seen during operation of the tool, that the control screw 89will advance as a unit with the gear case 18 as the latter is advancedby the piston. After the gear case has been advanced a predetermineddistance, a head 95 on the control screw will engage the bar support 87to cause axial advance of the actuating rod 83 and consequent actuationof the plunger 81 of the check cylinder. As the plunger is forced intothe check cylinder, the advancing speed of the piston and spindle isslowed. The time of cooperation of the control screwhead 95 with theactuating rod bar support 87 may be adjusted by making an axialadjustment of the control screw relative to the nut 92 so as to bringits head 95 selectively nearer or further away from the bar support 87.The limited axial movement allowed by slot 59 between the spindle andthe pinion shaft enables the socket to pick up the fastener withoutexerting excessive thrust upon the fastener. The check cylinder iscaused to function just prior to the socket engaging the fastener; andits operation is such that it permits the thrust upon the fastener toalways take out the limited axial movement allowed by slot 59.

It is apparent during operation of the tool that when the air feed tothe motor and the piston cylinder is shut off and the pressurizedcondition of the piston cylinder 63 is relaxed, further rotation andadvance of the spindle 17 will cease; and the spindle will be drawn fromthe work back to its normal position as the piston is retracted into itscylinder by the return spring 69. In this action, the control screw 89will be returned to its normal position to carry its head 95 away fromthe actuating rod bar support 87; and the plunger rod 81 of the checkcylinder will restore to normal in conventional manner by means of itsinternal spring mechanism as the control screw restores.

Limit signalling switches 96 and 9'! are provided to automaticallysignal to a conventional electrical control circuit CC completion ofboth the advance and retraction strokes in a cycle of the spindle. Theadvance limit switch 96 is mounted to the support block 84. It has arearwardly facing plunger 98. The retract limit switch 97 is alsomounted to block 84 and has a forwardly facing plunger 99. The means foractuating the advance limit switch includes a bracket 101 which isslidably mounted at its lower end 102 upon the check cylinder-actuatingrod 83. At its upper end, the bracket is slidably supported upon thecontrol screw 89 by means of a forwardly extending sleeve portion 103.The sleeve extends slidably into a complementary recess of the supportblock 84. The lower end of the bracket carries a plunger case 104containing a spring loaded pin 105, the head of which is axially alignedwith and abuts the plunger 98 of the advance limit switch. It can beseen that, as the spindle 17 is advanced by the piston-actuated gearcase 18, the head 95 of the control screw 89 eventually cooperates withthe actuating rod bar support 87. As the latter is forced forwardly bythe control screw, it eventually abuts the bracket 10! and slides itforwardly causing the pin [05 to be carried into abutment with theadvance switch limit plunger 98, whereupon the plunger 98 is actuatedsufiiciently to cause a signal to be transmitted to the control circuitCC indicating completion of the advance stroke. Spring 106 has a higherpreload than the force required to operate the plunger 98 of switch 96.The spring cushioned pin 105 is designed as a safety measure to avoiddamage to the switch which might otherwise occur as a result of someovertravel of pin 105 following its actuation of switch 96. The signalto the control circuit will be effected at about the time that the workor fastener is driven "home." A precise time for actuating the advancelimit switch 96 may be obtained by selective adjustment of the controlscrew 89 relative to its nut 92. When the signal is received by thecircuit, the latter responds in suitable manner to cause termination ofoperating airflow to the piston cylinder 63 and to the motor 22, and tocause relaxing of the pressurized condition of the piston cylinder. Whenthe circuit thus responds, the spindle [7, gear case 18 and piston 19will be returned to normal retracted position by the piston spring 69.

The retract signal switch 97 is designed to signal the circuit when thisnormal condition of the piston is reached. The means for actuating theretract signal switch includes a slide pin slidable through the rearwall l3 of the base. The slide pin has a forward end projecting into thechannel 14 of the base, which end is abuttable by a depending tail 108(FIGS. 1, 3) of the gear cue as the gear case is retracted by thepiston. The opposite end of the slide pin projects into a recess 109(FIG. 2) in the rear face of the wall [3 of the base. The switch plunger99 under the load of its internal spring abuts the end of the slide pinand normally biases the slide pin forwardly through the block to anonnal position in which a stop 11] on the slide pin abuts the bottom ofthe recess 109. It can be seen that in the retracting movement of thegear case by the piston, the tail end 108 of the case will eventuallyengage the slide pin 107 and actuate the plunger 99 of switch 97. Switch97 will be actuated at about the time that the projection 66 at the rearof the gear case abuts the stop 72 provided by the inner face of therear base wall 13. The control circuit will respond to the signaltransmitted by the actuated switch to indicate completion of the retractstroke by reconditioning the circuit preparatory to the next cycle ofthe tool. The switches 96 and 97 are conventional air switches. It isapparent that other conventional plunger type switches may be used.

lclaim:

l. In an air feed nut runner including a supporting base, a work spindlesupported in the base for axial movement toward and away from the workand for rotative movement to drive the work, a piston cylinder fixed tothe base, a piston reciprocable in the cylinder through an advancestroke and a return stroke, a gear case fixed to the piston for unitarymovement with the latter, means coupling the spindle with the gear casefor axial movement of the spindle as a unit with the gear case, a rotarymotor having a drive shaft, an elongated spline shaft extending axiallythrough the gear case, a slide coupling drivingly connecting the motordrive shaft with the spline shaft, a gear train carried by the gear casedrivingly connecting the spline shaft with the spindle and allowingaxial movement of the gear case along the spline shaft; and dampeningmeans actuable by the gear case at a predetermined point in the axialmovement of the spindle during an advance stroke of the piston to dampenthe advancing speed of the spindle; wherein the slide coupling has apair of V-slots, the spline shaft is axially slidable relative to thecoupling and has a head provided with a pair of wedge ribs slidablyreceived in the V-slots, and a spring load normally biases the splineshaft so as to seat the wedge ribs at the bottom of the V-slots, theaxial dimension of the wedge ribs being substantially less than that ofthe V-slots.

2. In an air feed nut runner as in claim 1, wherein the dampening meansis a check cylinder having an operating plunger, a slide rod issupported in the base for movement against the plunger to operate thecheck cylinder, and abutment means is carried by the gear case forengaging the slide rod and pressing it against the plunger.

3. In an air feed nut runner as in claim I, wherein the gear trainincludes a pinion shaft having a driving spline connection with thespindle.

4. In an air feed nut runner as in claim 1, wherein the means couplingthe spindle with the gear case includes a pinion shaft member of thegear train restrained in the gear case against relative axial movementhaving an axial sliding splined driving connection with the spindle, anabutment carried by the spindle engageable with a stop carried by thepinion shaft to prevent axial sliding release of the spindle from thepinion shaft, and a spring load between the pinion shaft and the spindlebiasing the spindle axially so as to engage the abutment with the stopand adapted to transmit axial movement of the gear case to the spindle.

5. in an air feed nut runner as in claim 4, wherein the abutment is apin extending transversely through a loss-motion slot in the pinionshaft, a forward wall of which slot defines the stop, and the pinionshaft is adapted during axial movement of the gear case on an advancestroke of the piston to advance relative to the spindle to the extent ofthe loss-motion of the slot upon the spindle encountering apredetermined degree of resistance to advancement by the work.

6. In an air feed nut runner as in claim 1, wherein the piston ispneumatically operable on its advance stroke and spring returnable onits retract stroke, the motor is air driven, and means is provided toconcurrently feed operating air to both the piston and motor.

7. In an air feed nut nmner as in claim 1, wherein means is provided tolimit the extent of the advance stroke of the piston, and other means isprovided to limit the extent of the retract stroke of the piston.

8. in an air feed nut runner as in claim 1, wherein a circuitcontrollingoperation of the nut runner is provided, an advance stroke limit switchis mounted to the supporting base, abutment means carried by the gearcase is cooperable with the limit switch at about the time the pistoncompletes its advance stroke to actuate the switch to transmit a signalto the circuit, a retract stroke limit switch is mounted to thesupporting base, and slide means is provided with which the gear case iscooperable at about the time the piston completes its retract stroke toactuate the retract limit switch to transmit a signal to the circuit.

9. In an air feed nut runner as in claim 8, wherein means is providedfor selectively adjusting the time of cooperation of the abutment meanswith the advance stroke limit switch.

10. in an air feed nut runner as in claim I, wherein the head of thespline shaft is axially displaceable from the bottom of the V-slots soas to carry the spline shaft forwardly against the bias of the springload upon the coupling experiencing a predetermined degree of overloadtorque.

UNITED STATES lA'lEN'l OFFICE CERTIFICATE OF CORRECTION Patent No.3576217 Dat d April l97 1 Inventor) Raymond J. Schaedler It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Column 2, line 62, "is located by the space 59." should read is locatedshort of a recessed bottom 58 of the spindle as indicated by the space59.

Signed and sealed this 17th day of August 1971.

(SEAL) Attest:

EDWARD M.FLETCHER,JR. WILLIAM E. SCHUYLER, JR. Attesting OfficerCommissioner of Patents OHM PO-HJSO (IO-69)

1. In an air feed nut runner including a supporting base, a work spindlesupported in the base for axial movement toward and away from the workand for rotative movement to drive the work, a piston cylinder fixed tothe base, a piston reciprocable in the cylinder through an advancestroke and a return stroke, a gear case fixed to the piston for unitarymovement with the latter, means coupling the spindle with the gear casefor axial movement of the spindle as a unit with the gear case, a rotarymotor having a drive shaft, an elongated spline shaft extending axiallythrough the gear case, a slide coupling drivingly connecting the motordrive shaft with the spline shaft, a gear train carried by the gear casedrivingly connecting the spline shaft with the spindle and allowingaxial movement of the gear case along the spline shaft; and dampeningmeans actuable by the gear case at a predetermined point in the axialmovement of the spindle during an advance stroke of the piston to dampenthe advancing speed of the spindle; wherein the slide coupling has apair of V-slots, the spline shaft is axially slidable relative to thecoupling and has a head provided with a pair of wedge ribs slidablyreceived in the V-slots, and a spring load normally biases the splineshaft so as to seat the wedge ribs at the bottom of the V-slots, theaxial dimension of the wedge ribs being substantially less than that ofthe V-slots.
 2. In an air feed nut runner as in claim 1, wherein thedampening means is a check cylinder having an operating plunger, a sliderod is supported in the base for movement against the plunger to operatethe check cylinder, and abutment means is carried by the gear case forengaging the slide rod and pressing it against the plunger.
 3. In an airfeed nut runner as in claim 1, wherein the gear train includes a pinionshaft having a driving spline connection with the spindle.
 4. In an airfeed nut runner as in claim 1, wherein the means coupling the spindlewith the gear case includes a pinion shaft member of the gear trainrestrained in the gear case against relative axial movement having anaxial sliding splined driving connection with the spindle, an abutmentcarried by the spindle engageable with a stop carried by the pinionshaft to prevent axial sliding release of the spindle from the pinionshaft, and a spring load between the pinion shaft and the spindlebiasing the spindle axially so as to engage the abutment with the stopand adapted to transmit axial movement of the gear case to the spindle.5. In an air feed nut runner as in claim 4, wherein the abutment is apin extending transversely through a loss-motion slot in the pinionshaft, a forward wall of which slot defines the stop, and the pinionshaft is adapted during axial movement of the gear case on an advancestroke of the piston to advance relativE to the spindle to the extent ofthe loss-motion of the slot upon the spindle encountering apredetermined degree of resistance to advancement by the work.
 6. In anair feed nut runner as in claim 1, wherein the piston is pneumaticallyoperable on its advance stroke and spring returnable on its retractstroke, the motor is air driven, and means is provided to concurrentlyfeed operating air to both the piston and motor.
 7. In an air feed nutrunner as in claim 1, wherein means is provided to limit the extent ofthe advance stroke of the piston, and other means is provided to limitthe extent of the retract stroke of the piston.
 8. In an air feed nutrunner as in claim 1, wherein a circuit-controlling operation of the nutrunner is provided, an advance stroke limit switch is mounted to thesupporting base, abutment means carried by the gear case is cooperablewith the limit switch at about the time the piston completes its advancestroke to actuate the switch to transmit a signal to the circuit, aretract stroke limit switch is mounted to the supporting base, and slidemeans is provided with which the gear case is cooperable at about thetime the piston completes its retract stroke to actuate the retractlimit switch to transmit a signal to the circuit.
 9. In an air feed nutrunner as in claim 8, wherein means is provided for selectivelyadjusting the time of cooperation of the abutment means with the advancestroke limit switch.
 10. In an air feed nut runner as in claim 1,wherein the head of the spline shaft is axially displaceable from thebottom of the V-slots so as to carry the spline shaft forwardly againstthe bias of the spring load upon the coupling experiencing apredetermined degree of overload torque.